The mass of a `._(3)^(7) Li` nucleus is `0.042 u` less than the sum of the masses of all its nucleons. The binding energy per nucleon of `._(3)^(7)Li` nucleus is nearly

Options

A. 46 MeV
B. 5.6 MeV
C. 3.9 MeV
D. 23 MeV

Explanation

For `""_(3)^(7)Li` nucleus,
Mass defect, `DeltaM=0.042u`
`because" "1u=931.5MeV//c^(2)`
`therefore" "DeltaM=0.042xx931.5MeV//c^(2)=39.1MeV//c^(2)`
Binding energy,
`E_(b)=DeltaMc^(2)=(39.1(MeV)/(c^(2)))c^(2)39.1MeV`
Binding energy per nucleon,
`E_(bn)=(E_(b))/(A)=(39.1MeV)/(7)~~ 5.6 MeV`